Adjustable mid air gap magnetic latching solenoid

0001This application claims the priority and benefit of U.S. Provisional Patent Application 60/907,972, filed Apr. 25, 2007, entitled “ADJUSTABLE MID AIR GAP MAGNETIC LATCHING SOLENOID”; and U.S. Provisional Patent Application 60/996,888, filed Dec. 10, 2007, entitled “ADJUSTABLE MID AIR GAP MAGNETIC LATCHING SOLENOID”; both of which are incorporated herein by reference in their entirety.

BACKGROUND

0002I. Technical Field

0003This invention pertains to the field of solenoids, and particularly to magnetic latching solenoids.

0004II. Related Art and Other Considerations

0005A typical solenoid has a moveable member which is connected to or integral with a plunger or piston. The moveable piston or plunger, which can be in the form of an output shaft, is the serving or working element/aspect of the solenoid that can be employed in any of various applications or utilizations.

0006One type of solenoid is a “power stroking” or “power on” solenoid. In a natural state of a power stroking solenoid, the solenoid moveable member is separated by an air gap from a solenoid stationary member. The solenoid also has a coil or the like which, when energized, creates a magnetic flux. The magnetic flux generated by the coil results in the moveable member being electromagnetically attracted to the stationary member(s). Depending on the positioning and configuration of the piston relative to the moveable member, attraction of the moveable member toward the stationary member can cause the piston to be retracted or extended relative to its original position. The moveable member is held in place (in attraction) to the stationary member until power is removed from the coil. When power is removed, the moveable member returns to its original separated position (e.g., the moveable member is again separated from the stationary member by an air gap). Return of the moveable member to its original position is often facilitated by a spring or the like. An example power stroking solenoid which operates generally in accordance with the foregoing but with piston extension upon power stroking is shown in U.S. Pat. No. 4,812,884 to Mohler, entitled “Three-Dimensional Double Air Gap High Speed Solenoid”, which is incorporated herein by reference.

0007In contrast to a power stroking solenoid, a “holding” solenoid starts with a minimal air gap between the moveable member and the stationary member. When the holding solenoid is powered (e.g. by energization of a solenoid coil), the electromagnetic attractive forces hold the moveable member rigidly to the stationary member.

0008A magnetic latching or “maglatch solenoid” is a derivative of the “holding solenoid” and further includes an internally compressed spring and a permanent magnet. In its natural (and unpowered) state, the moveable member is magnetically latched to the stationary member while compressing the spring. When powered, the permanent magnet's holding force is reduced sufficiently that the spring can force the moveable member away from the stationary member.

0009Thus, a magnetic latching solenoid typically comprises a coil, a spring, a permanent magnet, and at least two metal components that provide a magnetic path for the magnet's flux. The spring is located between the two metal components, one of which contains the permanent magnet. As the one metal component moves toward the other, the spring is compressed. When the metal parts are brought within close proximity of each other, they latch together since the magnetic attracting force between the two metal components is greater than the opposing mechanical spring force. To unlatch (release) a magnetically latched solenoid, current (power) is applied to the coil housed within the metal components. This release power provides sufficient magnetic flux to offset/cancel the permanent magnet's flux, such that the spring force is now greater than the magnetic attracting force between the two metal components. With the magnetic attracting force thus overcome, the metal components separate (unlatch). Applications for this type of solenoid include circuit breakers, door locks, brake locks, etc.

0010As the moving metal component is re-latched to its mating stationary metal component during repeated actuations, variations in the magnetic circuit and air gaps between the metal components of typical magnetic latching solenoids result in release power variations that are unacceptable to the customer. Release power is the power (current and voltage) applied to the coil that allows the moveable member to be released from the stationary member. The release power variations can result in piston action that is non-uniform (e.g., with respect to one or more of piston position/placement, piston actuation power, or piston speed/response).

0011Since air gaps reduce magnetic efficiency when latched, a “zero” air gap magnetic latching solenoid is optimal. The location and size of air gaps, e.g., gaps between the moveable member and the stationary member, significantly affect the solenoid's performance. Even the smallest air gap is deleterious to the electromagnetic flux fields and flux paths which travel through the stationary member and the moveable member. Although a zero air gap is not yet achievable with contemporary designs, the air gap should be kept as small as possible.

BRIEF SUMMARY

0012In one of its aspects the technology concerns a magnetic latching solenoid. The solenoid comprises a housing, a moveable magnetically permeable member, a stationary magnetic assembly, a counter flux generator; and, a spring.

0013The housing comprises a housing first end. The housing at least partially defines a housing cavity. The moveable magnetically permeable member is configured to translate at least partially within the housing from a latched position to a stroked position along an axis. The moveable member comprises a plunger, a housing-confined shoulder surface, and a moveable mating surface. The plunger is extendable through an aperture in the housing first end. The housing-confined shoulder surface is contiguous to the plunger and lies at least partially in a first plane transverse to the axis when in the latched position. The moveable mating surface lies at least partially in a second plane transverse to the axis when in the latched position.

0014The stationary magnetic assembly is situated at least partially in the housing and in the housing cavity. The stationary magnetic assembly comprises a stationary magnetically permeable member and a permanent magnet. The stationary magnetically permeable member comprises at least one magnetized mating surface. The permanent magnet is configured to generate a permanent magnetic flux field in the stationary magnetically permeable member and in the moveable magnetically permeable member. The flux field generated by the permanent magnet and conducted through a magnetic circuit is sufficient to retain the moveable magnetically permeable member essentially in contact with the stationary magnetically permeable member at an air gap interface between the stationary magnetically permeable member and the moveable magnetically permeable member when in the latched position (absent a counter flux field which overcomes the permanent magnetic flux field).

0015The moveable magnetically permeable member and members of the stationary magnetic assembly comprise a magnetic circuit for conducting magnetic flux. The members of the stationary magnetic assembly that comprise the magnetic circuit (also known as stationary circuit members) include a stationary case, the stationary magnetically permeable member (also known as a pole member); the permanent magnet, and a plate. The stationary magnetically permeable member is located between the moveable magnetically permeable member and the permanent magnet with respect to the axis. An axial extent of the moveable magnetically permeable member along the axis from the shoulder surface to the moveable mating surface is essentially the same as an axial extent of the stationary magnetic assembly (e.g., the stationary circuit members) along the axis.

0016The spring is configured to bias the moveable magnetically permeable member away from the stationary magnetically permeable assembly when a counter flux generated by the counter flux generator overcomes the permanent magnetic flux.

0017In an example embodiment, the housing cavity is essentially open opposite the housing first end, and wherein the solenoid further comprises a plate and a cover. The plate has a major dimension which is transverse to the axis. The cover is configured to enclose the housing cavity. The housing and the cover are configured whereby the moveable magnetically permeable member, the stationary magnetically permeable member, the permanent magnet, and the plate can be axially aligned in this order within a volume defined by the housing and the cover.

0018In an example embodiment, the stationary magnetically permeable member comprises two magnetized mating surfaces. The stationary magnetically permeable member comprises a stationary case member and a pole member. The case member at least partially defines a case cavity and comprises one magnetized mating surface. The pole member is configured for selective positioning within the case cavity along the axis and thereby provides another magnetized mating surface independently positionable along the axis relative to the magnetized mating surface of the case member. In an example implementation, at least portions of the field generator, the pole member (e.g., stationary magnetically permeable member), and the permanent magnet are transversely interior to the stationary case member.

0019In an example implementation, the moveable magnetically permeable member comprises an axially extending central portion and an axially extending peripheral portion. The moveable magnetically permeable member comprises two moveable mating surfaces, a first moveable mating surface provided on the axially extending central portion and a second moveable mating surface provided on the axially extending peripheral portion.

0020In an example implementation, a moveable member cavity is defined between an axially extending central portion and an axially extending peripheral portion of the moveable magnetically permeable member. A stationary cavity is defined between the stationary case member and the pole member. The moveable member cavity and the stationary cavity are axially aligned. The counter flux generator is positioned at least partially in the moveable member cavity and the stationary cavity.

0021In an example implementation, the spring comprises a conical spring situated in the moveable member cavity. The conical spring has a first end coil lying in a first spring end plane and a second end coil lying in a second spring end plane. The second end coil has a greater diameter than the first end coil. The second end coil contacts a radially extending interior surface of the moveable magnetically permeable member

0022In an example implementation, the flux generator comprises a bobbin frame. The bobbin frame comprises an axially extending bobbin flange and a transverse bobbin flange which extend into the moveable member cavity. The first end coil of the spring is separated from the central core of the moveable magnetically permeable member by the axially extending bobbin flange.

0023In another aspect, the technology concerns a magnetic latching solenoid comprising an essentially open-mouthed housing, a moveable magnetically permeable member, a stationary magnetic assembly, a counter flux generator; and, a spring.

0024The housing comprises a housing first end and at least partially defines a housing cavity. The housing cavity has an essentially open housing mouth (which is essentially open opposite the housing first end).

0025The moveable magnetically permeable member configured to translate at least partially within the housing from a latched position to a stroked position along an axis. The moveable magnetically permeable member comprises a moveable mating surface at least partially lying in a plane transverse to the axis when in the latched position.

0026The stationary magnetic assembly is situated at least partially in the housing and in the cavity and configured for insertion through the housing mouth. The stationary magnetic assembly comprises a stationary case member, a pole member, a permanent magnet, and a plate. The stationary case member at least partially defines a case cavity and comprises a peripheral magnetized mating surface. The pole member comprises another, e.g., central, magnetized mating surface. The permanent magnet is configured to generate a permanent magnetic flux field in the pole member, in the moveable magnetically permeable member, and in the stationary case member which is sufficient to retain the moveable magnetically permeable member essentially in contact with the stationary magnetically permeable assembly at an air gap interface between the stationary magnetically permeable assembly and the moveable magnetically permeable member when in the latched position (absent a counter flux field which overcomes the permanent magnetic flux field).

0027The pole member is located between the moveable magnetically permeable member and the permanent magnet with respect to the axis. The pole member comprises a configuration for being selective positioned through the housing mouth and within the case cavity along the axis whereby the central magnetized mating surface on the pole member is positionable along the axis relative to the moveable mating surface in a manner that is independent of the first magnetized mating surface.

0028The spring is configured to bias the moveable magnetically permeable member away from the stationary magnetically permeable assembly when a counter flux generated by the counter flux generator overcomes the permanent magnetic flux.

0029In an example implementation, the stationary magnetic assembly is distinct from the housing, and the housing is non-magnetically permeable.

0030Another aspect of the technology includes a method of making a magnetically latched solenoid. The method begins with providing a housing. The housing comprises a housing first end and at least partially defines a housing cavity through which an axis extends (which is essentially open opposite the housing first end). Moreover, the housing cavity having an essentially open housing mouth.

0031The method also includes inserting, into the housing cavity, a moveable magnetically permeable member and a spring. The moveable magnetically permeable member comprises an axially extending central portion and an axially extending peripheral portion. A moveable member cavity is defined between the axially extending central portion and the axially extending peripheral portion. The spring is provided for biasing the moveable magnetically permeable member toward the housing first end.

0032The method further includes inserting, through the housing mouth and into the housing cavity, the following: a pole member, a counter flux generator, a stationary case member; and, a permanent magnet. The pole member comprises a pole member mating surface. The counter flux generator is inserted at least partially into the moveable member cavity. The stationary case member at least partially defines a case cavity and comprises a peripheral magnetized mating surface. Upon insertion of the stationary case member, the case cavity is occupied at least partially by the counter flux generator and the pole member.

0033The method also includes applying a force which acts on the pole member for driving the pole member mating surface toward the moveable magnetically permeable member and thereby adjusting a central air gap between the pole member mating surface and the moveable magnetically permeable member, the central air gap being adjusted independently of a peripheral air gap between the peripheral mating surface of the stationary case member and the moveable magnetically permeable member.

0034In one example embodiment and mode, the method comprises inserting certain elements through the housing mouth in a predefined order. These elements are stationary circuit elements which happened to be axially aligned, e.g., the pole member, the permanent magnet, and the plate. The force is applied to a selected one of these (e.g., axially aligned) elements upon insertion of the selected one of the axially aligned elements into the housing cavity; and thereafter any remaining one(s) of the selected are inserted into the housing cavity. In an example implementation, the predefined order comprises: the pole member, the permanent magnet; and the plate. In this example implementation, the act of applying the force comprises applying the force to the plate, whereby the force acts consecutively through the plate, the permanent magnet, and the pole member

0035An example mode of the method further comprises inserting in order through the housing mouth the pole member, the counter flux generator, the stationary case member, the permanent magnet, and the plate.

0036This technology therefore provides an approach that combines both a “zero” air gap and mid air gap design to maximize the solenoid's magnetic efficiency while also providing a more consistent magnetic circuit when the metal components latch for improved solenoid performance, i.e. a higher magnetic latching force.

0037The technology provides, e.g.: 1) a more efficient magnetic circuit to increase the magnetic latching force; 2) a design that virtually eliminates all air gaps by employing an adjustable pole piece; and, 3) a robust, low-cost and easily assembled design with flexibility for various power levels, mounting schemes and output adaptors.

BRIEF DESCRIPTION OF THE DRAWINGS

0038The foregoing and other objects, features, and advantages of the invention will be apparent from the following more particular description of preferred embodiments as illustrated in the accompanying drawings in which reference characters refer to the same parts throughout the various views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention.

0039<figref idref="DRAWINGS">FIG. 1</figref> is a cross sectioned view of a first example embodiment magnetic latching solenoid.

0040<figref idref="DRAWINGS">FIG. 2</figref> is an exploded view of the example embodiment of <figref idref="DRAWINGS">FIG. 1</figref>.

0041<figref idref="DRAWINGS">FIG. 3</figref> is left end perspective view of the example embodiment of <figref idref="DRAWINGS">FIG. 1</figref>.

0042<figref idref="DRAWINGS">FIG. 4</figref> is right end view perspective of the example embodiment of <figref idref="DRAWINGS">FIG. 1</figref>.

0043<figref idref="DRAWINGS">FIG. 5</figref> is a flowchart depicting representative, basic acts or steps comprising a method of making a magnetic latching solenoid.

0044<figref idref="DRAWINGS">FIG. 6</figref> is a cross sectioned view of another example embodiment magnetic latching solenoid.

0045<figref idref="DRAWINGS">FIG. 7</figref> is a cross sectioned view of another example embodiment magnetic latching solenoid.

0046<figref idref="DRAWINGS">FIG. 8</figref> is a cross sectioned view of another example embodiment magnetic latching solenoid.

0047<figref idref="DRAWINGS">FIG. 9</figref> is a cross sectioned view of another example embodiment magnetic latching solenoid.

0048<figref idref="DRAWINGS">FIG. 10</figref> is a cross sectioned view of another example embodiment magnetic latching solenoid.

0049<figref idref="DRAWINGS">FIG. 11</figref> is a cross sectioned schematic view of the example embodiment magnetic latching solenoid of <figref idref="DRAWINGS">FIG. 10</figref>, showing selected components advantageous for illustrating structure and retention of a conical spring thereof.

0050<figref idref="DRAWINGS">FIG. 12</figref> is a cross sectioned view of another example embodiment magnetic latching solenoid.

0051<figref idref="DRAWINGS">FIG. 13A</figref> is a side sectioned view of portions of another example embodiment magnetic latching solenoid; <figref idref="DRAWINGS">FIG. 13B</figref> is a top view of the example embodiment of <figref idref="DRAWINGS">FIG. 13A</figref>.

DETAILED DESCRIPTION

0052In the following description, for purposes of explanation and not limitation, specific details are set forth such as particular architectures, interfaces, techniques, etc. in order to provide a thorough understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced in other embodiments that depart from these specific details. That is, those skilled in the art will be able to devise various arrangements which, although not explicitly described or shown herein, embody the principles of the invention and are included within its spirit and scope. In some instances, detailed descriptions of well-known devices, circuits, and methods are omitted so as not to obscure the description of the present invention with unnecessary detail. All statements herein reciting principles, aspects, and embodiments of the invention, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Additionally, it is intended that such equivalents include both currently known equivalents as well as equivalents developed in the future, i.e., any elements developed that perform the same function, regardless of structure.

0053<figref idref="DRAWINGS">FIG. 1</figref> shows a first example embodiment of magnetic latching solenoid <b>20</b>. The magnetic latching solenoid <b>20</b> comprises housing <b>22</b>, moveable magnetically permeable member <b>24</b>, stationary magnetic assembly <b>26</b>, counter flux generator <b>28</b>; and, spring <b>30</b>. <figref idref="DRAWINGS">FIG. 2</figref> is an exploded view of the example embodiment of <figref idref="DRAWINGS">FIG. 1</figref>. <figref idref="DRAWINGS">FIG. 3</figref> and <figref idref="DRAWINGS">FIG. 4</figref> are respective left end perspective and right end perspective views of the example embodiment of <figref idref="DRAWINGS">FIG. 1</figref> as assembled.

0054The housing <b>22</b> has an essentially hollow cylindrical shape defined by housing end wall <b>32</b> at a first housing end and by a circumferentially extending housing sidewall <b>34</b>. The cylindrical volume defined by housing <b>22</b> has cylindrical axis <b>35</b>. The housing end wall <b>32</b> has plunger aperture <b>36</b> extending there through along axis <b>35</b>. The housing <b>22</b> thus at least partially defines a housing cavity <b>37</b> having an essentially open housing mouth <b>38</b>.

0055The moveable magnetically permeable member <b>24</b> is configured to translate at least partially within housing <b>22</b> from a latched position to a stroked position along axis <b>35</b>. <figref idref="DRAWINGS">FIG. 1</figref> shows moveable magnetically permeable member <b>24</b> in its latched position in which moveable magnetically permeable member <b>24</b> is attracted to stationary magnetic assembly <b>26</b>. The moveable member <b>24</b> comprises plunger <b>40</b>, housing-confined shoulder surface <b>42</b>, and one or more moveable mating surfaces which are represented as moveable mating surface <b>44</b>. The moveable magnetically permeable member <b>24</b> has an essentially disk shape. An outer diameter of moveable magnetically permeable member <b>24</b> at peripheral sidewall <b>46</b> is of a dimension to enable moveable magnetically permeable member <b>24</b> to translate in housing cavity <b>37</b> along cylindrical axis <b>35</b> in sliding contact with the interior surface of housing sidewall <b>34</b>. The upper and lower end walls of moveable magnetically permeable member <b>24</b>, being transverse or orthogonal to cylindrical axis <b>35</b>, comprise housing-confined shoulder surface <b>42</b> and moveable mating surface <b>44</b>, respectively.

0056Plunger <b>40</b> is extendable through aperture <b>36</b> in the housing first end, e.g., in housing end wall <b>32</b>. Plunger <b>40</b> can be integrally formed with moveable magnetically permeable member <b>24</b> or affixed or otherwise connected to moveable magnetically permeable member <b>24</b>. The housing-confined shoulder surface <b>42</b> is contiguous to plunger <b>40</b> and lies at least partially in a first plane transverse to axis <b>35</b> when in the latched position. The housing-confined shoulder surface <b>42</b> is incapable of extending through, and does not extend through, aperture <b>36</b> in housing first end <b>32</b>. Thus, housing-confined shoulder surface <b>42</b> has a greater extent than plunger <b>40</b> in the first plane in which moveable magnetically permeable member <b>24</b> lies.

0057The stroke range of plunger <b>40</b> is shown by the arrow labeled “Stroke”. The extent of the stroke is defined by the volume in housing cavity <b>37</b> that exists between the inner wall of housing end wall <b>32</b> and the housing-confined shoulder surface <b>42</b> when the moveable magnetically permeable member <b>24</b> is in the latched position. Since this stroke range is dependent upon the geometry and sizing, the stroke range can vary according to application and user requirements.

0058In an example implementation, as seen from the perspective of stationary magnetic assembly <b>26</b> the moveable magnetically permeable member <b>22</b> comprises axially extending central portion <b>47</b> and axially extending peripheral portion <b>48</b>. A toroid shaped moveable member cavity <b>49</b> is formed between axially extending central portion <b>47</b> and axially extending peripheral portion <b>48</b>. As explained subsequently, moveable member cavity <b>49</b> is at least partially occupied by counter flux generator <b>28</b>.

0059Since moveable magnetically permeable member <b>24</b> comprises both axially extending central portion <b>47</b> and axially extending peripheral portion <b>48</b>, moveable mating surface <b>44</b> of moveable magnetically permeable member <b>24</b> actually comprises two moveable mating surfaces: a first moveable mating surface <b>50</b> provided on axially extending central portion <b>47</b> and a second moveable mating surface <b>52</b> provided on axially extending peripheral portion <b>48</b>. Both first moveable mating surface <b>50</b> and second moveable mating surface <b>52</b> are annular rings (e.g., toroidal in shape), with the outer diameter of first moveable mating surface <b>50</b> being less than the inner diameter of second moveable mating surface <b>52</b>. The moveable mating surface <b>44</b> (with its two components first moveable mating surface <b>50</b> and second moveable mating surface <b>52</b>) lies at least partially in a second plane transverse to axis <b>35</b> when moveable magnetically permeable member <b>24</b> is in the latched position.

0060The moveable magnetically permeable member and members of the stationary magnetic assembly comprise a magnetic circuit for conducting magnetic flux. The members of the stationary magnetic assembly that comprise the magnetic circuit (known as stationary circuit members) include stationary case <b>60</b>; stationary magnetically permeable member <b>62</b> (also known as pole member <b>62</b>); permanent magnet <b>64</b>, and plate <b>65</b>.

0061The stationary magnetic assembly <b>26</b> is situated at least partially within housing <b>22</b> and thus in housing cavity <b>37</b>. The stationary magnetically permeable member <b>62</b> comprises (on its top transverse wall) a central magnetized mating surface <b>66</b>. A stationary cavity <b>67</b> is defined between an exteriorly positioned stationary case member <b>60</b> on the one side, and pole member <b>62</b> and permanent magnet <b>64</b> on an interior side.

0062The permanent magnet <b>64</b> generates a permanent magnetic flux field in stationary magnetically permeable member <b>26</b> and in moveable magnetically permeable member <b>24</b>. The flux field generated by permanent magnet <b>64</b> is sufficient to retain moveable magnetically permeable member <b>24</b> essentially in contact with stationary magnetically permeable member <b>26</b> at an air gap interface <b>70</b> between stationary magnetically permeable member <b>26</b> and moveable magnetically permeable member <b>24</b> when in the latched position, e.g., the position shown in <figref idref="DRAWINGS">FIG. 1</figref> in which a counter flux field is not applied to overcome the permanent magnetic flux field.

0063The stationary magnetically permeable member <b>62</b>, i.e., pole member <b>62</b>, is located between moveable magnetically permeable member <b>24</b> and permanent magnet <b>64</b> with respect to axis <b>35</b>. Preferably, the axial extent of moveable magnetically permeable member <b>24</b> along axis <b>35</b> from shoulder surface <b>42</b> to moveable mating surface <b>44</b> is essentially the same as the axial extent of stationary magnetic assembly <b>26</b> (including stationary case <b>60</b>, stationary magnetically permeable member <b>62</b>, and permanent magnet <b>64</b>) along axis <b>35</b>. By “essentially the same” is meant that the axial extent of moveable magnetically permeable member <b>24</b> along axis <b>35</b> from shoulder surface <b>42</b> to moveable mating surface <b>44</b> is within twenty percent of an axial extent of stationary magnetic assembly <b>26</b> (including stationary case <b>60</b>, stationary magnetically permeable member <b>62</b>, and permanent magnet <b>64</b>) along axis <b>35</b>. That is, the axial extent of moveable magnetically permeable member <b>24</b> is essentially the same as the axial extent of the stationary magnetic assembly <b>26</b>, plus or minus twenty percent.

0064As explained subsequently, the substantially equal extent of moveable magnetically permeable member <b>24</b> and stationary magnetic assembly <b>26</b> along cylindrical axis <b>35</b> results in air gap interface <b>70</b> being essentially mid-way between the opposite axial extremities of moveable magnetically permeable member <b>24</b> and stationary magnetic assembly <b>26</b>, e.g., mid-way between housing-confined shoulder surface <b>42</b> of moveable magnetically permeable member <b>24</b> and the outer transverse surface of plate <b>65</b>. Thus, the mid air gap interface <b>70</b> is located at essentially the halfway or midpoint of the complete magnetic circuit. The fact that the air gap is mid-way facilitates the flux path at air gap interface <b>70</b> as being essentially parallel to the direction of cylindrical axis <b>35</b>, which (in the case of permanent magnet <b>64</b>) provides a greater attracting or holding force by stationary magnetic assembly <b>26</b> for moveable magnetically permeable member <b>24</b>. It is thus highly desirable, and accomplished by the present technology, to have the flux lines aligned at the air gap in an axial orientation, e.g., parallel to axis <b>35</b>. When the axial extent of moveable magnetically permeable member <b>24</b> (along axis <b>35</b> from shoulder surface <b>42</b> to moveable mating surface <b>44</b>) is more than twenty percent of an axial extent of stationary magnetic assembly <b>26</b>, the attracting or holding force of the permanent magnet is diminished by more than five percent. Thereafter there is increasing diminished holding force with increasingly larger discrepancies of axial extents of the magnetically permeable member and the stationary magnetic assembly. When the axial extent of moveable magnetically permeable member <b>24</b> (along axis <b>35</b> from shoulder surface <b>42</b> to moveable mating surface <b>44</b>) is within ten percent of an axial extent of stationary magnetic assembly <b>26</b>, the attracting or holding force is diminished by about one percent or less.

0065The counter flux generator <b>28</b> of the magnetic latching solenoid <b>20</b> of <figref idref="DRAWINGS">FIG. 1</figref> comprises bobbin <b>72</b>. The counter flux generator <b>28</b>. e.g., bobbin <b>72</b>, is positioned at least partially in moveable member cavity <b>49</b> and at least partially in stationary cavity <b>67</b>, the moveable member cavity <b>49</b> and stationary cavity <b>67</b> being axially aligned and sized to receive bobbin <b>72</b>. The bobbin <b>72</b> has an essentially hollow cylindrical shape and as such has axially extending bobbin cylinder wall <b>74</b> about which a coil of wiring <b>74</b> is exteriorly wound. The coil <b>76</b> is captured between bobbin upper transverse flange <b>77</b> and bobbin lower transverse flange <b>78</b>. The coil <b>76</b> terminates in a lead wires <b>79</b> or the like which extends radially through a port in stationary case <b>60</b> and housing sidewall <b>34</b>.

0066As explained above, stationary magnetically permeable assembly <b>26</b> comprises, e.g., stationary case member <b>60</b> and pole member <b>62</b>, e.g., stationary magnetically permeable member <b>62</b>. The stationary case <b>60</b> has an interior wall which at least partially defines case cavity <b>80</b>. On its upper end the stationary case <b>60</b> comprises peripheral magnetized mating surface <b>82</b>. Thus, in the example embodiment of <figref idref="DRAWINGS">FIG. 1</figref>, stationary magnetically permeable assembly <b>26</b> comprises two magnetized mating surfaces, i.e., central magnetized mating surface <b>66</b> and peripheral magnetized mating surface <b>82</b>.

0067As explained in more detail below, pole member <b>62</b> is configured for selective positioning within case cavity <b>80</b> and along axis <b>35</b>, and thereby provides magnetized mating surface <b>50</b> independently positionable relative to magnetized mating surface <b>66</b> along axis <b>35</b>. In an example implementation, at least portions of counter flux generator <b>28</b>, pole member <b>62</b>, and permanent magnet <b>64</b> are transversely interior to stationary case member <b>60</b>. In other words, as shown in <figref idref="DRAWINGS">FIG. 1</figref>, the positioning of magnetized mating surface <b>50</b> along the axis <b>35</b> is dependent only on the location of the movable magnetic mating surface <b>44</b>.

0068Spring <b>30</b> is configured to bias moveable magnetically permeable member <b>24</b> away from stationary magnetically permeable assembly <b>26</b> when a counter flux generated by counter flux generator <b>28</b> overcomes the permanent magnetic flux generated by permanent magnet <b>64</b>. In the embodiment shown in <figref idref="DRAWINGS">FIG. 1</figref>, spring <b>30</b> is retained partially in a central cavity <b>90</b> of moveable magnetically permeable member <b>24</b> (at the center of axially extending central portion <b>47</b>) and retained partially in a central cavity <b>92</b> of stationary magnetically permeable member <b>62</b>. The central cavity <b>90</b> and central cavity <b>92</b> are aligned in the direction of cylindrical axis <b>35</b>. Further, in the example embodiment of <figref idref="DRAWINGS">FIG. 1</figref>, spring <b>30</b> surrounds plunger guide post <b>94</b>. The plunger guide post <b>94</b> extends centrally through plunger <b>40</b> and is centrally rooted in moveable magnetically permeable member <b>24</b>, and in particular in axially extending central portion <b>47</b>.

0069As shown in the example embodiment of <figref idref="DRAWINGS">FIG. 1</figref>, the housing mouth <b>38</b> of housing cavity <b>37</b> is essentially open opposite the housing first end, e.g., opposite housing end wall <b>32</b>. The magnetic latching solenoid <b>20</b> of <figref idref="DRAWINGS">FIG. 1</figref> further comprises plate <b>65</b>. The plate <b>65</b> has a major dimension which is transverse to axis <b>35</b>. After insertion of the permanent magnet <b>64</b> into housing cavity <b>37</b>, insertion of plate <b>65</b> into housing cavity <b>37</b> provides a transverse end surface that (in the illustrated embodiment) happens to be flush with the transversely extending flange <b>98</b> of stationary case <b>60</b>. The flushness of plate <b>65</b> is not critical, as the end of the solenoid can have differing configurations in differing embodiments. Plate <b>65</b> is significant in, e.g., being one of the elements that comprises the stationary circuit necessary for conducting the magnetic flux. The plate <b>65</b> is thus the last element to be inserted into housing cavity <b>37</b> for completing the magnetic circuit and, in the illustrated embodiment, to close completely housing mouth <b>38</b>, after various components of magnetic latching solenoid <b>20</b> have been inserted into housing cavity <b>37</b> in a manner such as that hereinafter described. Thus, housing <b>22</b> and plate <b>65</b> are configured whereby moveable magnetically permeable member <b>24</b>, case member <b>60</b>, permanent magnet <b>64</b>, and plate <b>65</b> can be axially aligned in this order within a volume defined by housing <b>22</b> and the plate <b>65</b>.

0070<figref idref="DRAWINGS">FIG. 1</figref> thus shows a cross-sectional view of magnetic latching solenoid <b>20</b> and also illustrates magnetic flux path FP. With moveable magnetically permeable member <b>24</b> latched against stationary magnetic assembly <b>26</b>, the spring <b>30</b> is compressed and the magnetic flux that originates from permanent magnet <b>64</b> “circulates” through the metal components as shown by the arrows labeled FP. Whereas typical magnetic latching solenoids have their primary air gap (interface between the moving and stationary component(s)) near the end of the solenoid, e.g., closer to housing end wall <b>32</b>, in the present technology the primary air gap <b>70</b> is located in the middle of the solenoid (e.g., in the middle of the metallic and magnetically permeable components comprising moveable magnetically permeable member <b>24</b> and stationary magnetic assembly <b>26</b> as explained above), thereby allowing for a more efficient magnetic circuit.

0071<figref idref="DRAWINGS">FIG. 1</figref> also identifies five important interfaces between mating components, i.e., interfaces at which air gaps need to be minimized (since air gaps reduce the magnetic efficiency of the solenoid). These five air gaps are labeled as AG<b>1</b>-AG<b>5</b>, respectively. A first air gap (AG<b>1</b>) is between permanent magnet <b>64</b> and pole member <b>62</b>. A second air gap (AG<b>2</b>) is between moveable mating surface <b>50</b> of axially extending central portion <b>47</b> of moveable magnetically permeable member <b>24</b> and magnetized mating surface <b>66</b> of pole member <b>62</b>. A third air gap (AG<b>3</b>) is between second moveable mating surface <b>52</b> of axially extending peripheral portion <b>48</b> of moveable magnetically permeable member <b>24</b> and second magnetized mating surface <b>82</b> of stationary case <b>60</b>. A fourth air gap (AG<b>4</b>) is between the axially extending surfaces of stationary case <b>60</b> (which, e.g., define case cavity <b>80</b>) and elements within case cavity <b>80</b>, e.g., plate <b>65</b>. A fifth air gap (AG<b>5</b>) is between plate <b>65</b> and permanent magnet <b>64</b>.

0072Thus, as seen in <figref idref="DRAWINGS">FIG. 1</figref>, the two air gap interfaces AG<b>2</b> and AG<b>3</b> extend in a radial direction which is orthogonal to axis <b>35</b>. The two air gap interfaces AG<b>2</b> and AG<b>3</b> are spaced apart from one another in the radial direction. The two air gap interfaces AG<b>2</b> and AG<b>3</b> are separated in the radial direction by the counter flux generator <b>28</b>.

0073A challenge with a mid air gap solenoid is the air gap interface <b>70</b> between moveable magnetically permeable member <b>24</b> and stationary magnetic assembly <b>26</b>. In the example double ring configuration illustrated in <figref idref="DRAWINGS">FIG. 1</figref>, air gap interface <b>70</b> actually comprises two air gaps: air gap AG<b>2</b> (between moveable mating surface <b>50</b> of axially extending central portion <b>47</b> of moveable magnetically permeable member <b>24</b> and magnetized mating surface <b>66</b> of pole member <b>62</b>) and air gap AG<b>3</b> (between second moveable mating surface <b>52</b> of axially extending peripheral portion <b>48</b> of moveable magnetically permeable member <b>24</b> and second magnetized mating surface <b>82</b> of stationary case <b>60</b>). That is, the mating surface for both moveable magnetically permeable member <b>24</b> and stationary magnetic assembly <b>26</b> comprise both an outer ring and an inner ring that contact each other's surface respectively and simultaneously. The flatness between the outer ring and the inner ring's surface for each component contributes to a potential air gap of several thousandths of an inch, which can significantly degrade the magnetic efficiency of the solenoid. This technology eliminates that concern by having an adjustable pole piece <b>62</b> centrally located within stationary magnetic assembly <b>26</b>. The ability to independently locate pole member <b>62</b> ensures contact with the inner ring of moveable magnetically permeable member <b>24</b> (e.g., moveable mating surface <b>50</b> of axially extending central portion <b>47</b>) during the build process. The build process, e.g., a method for making a magnetic latching solenoid, is described further herein. The contact at air gap AG<b>3</b> between the outer rings of moveable magnetically permeable member <b>24</b> and stationary magnetic assembly <b>26</b> is also ensured during the build process. Thus the air gaps associated with the mid air gap solenoid have been virtually eliminated.

0074Another aspect of the technology includes a method of making a magnetically latched solenoid, e.g., a solenoid build process. Basic acts or steps comprising the method are illustrated in simplified, representative fashion in <figref idref="DRAWINGS">FIG. 5</figref>. Although the method of <figref idref="DRAWINGS">FIG. 5</figref> is discussed in context of the structure of the example embodiment of <figref idref="DRAWINGS">FIG. 1</figref>, it will be appreciated that the method is not limited to the <figref idref="DRAWINGS">FIG. 1</figref> embodiment but also encompasses other embodiments such as those also illustrated or otherwise embraced herein.

0075Act <b>5</b>-<b>1</b> depicts providing a housing, such as housing <b>22</b>. As indicated previously, in one example illustrated embodiment housing <b>22</b> comprises housing end wall <b>32</b> provided with plunger aperture <b>36</b>. The housing <b>22</b> at least partially defines housing cavity housing cavity <b>37</b> through which axis <b>35</b> extends. The housing cavity <b>37</b> is essentially open opposite housing first end <b>32</b>, e.g., comprises an essentially open housing mouth <b>38</b>.

0076The method also includes, as act <b>5</b>-<b>2</b>, inserting, into housing cavity <b>37</b>, the moveable magnetically permeable member <b>24</b> and spring <b>30</b>. In one example illustrated embodiment moveable magnetically permeable member <b>24</b> comprises the axially extending central portion <b>47</b> and the axially extending peripheral portion <b>48</b>. A moveable member cavity <b>49</b> is defined between the axially extending central portion <b>47</b> and axially extending peripheral portion <b>48</b>.

0077The method further includes, as act <b>5</b>-<b>3</b>, inserting, through housing mouth <b>38</b> and into the housing cavity <b>37</b>, the following: pole member <b>62</b>, counter flux generator <b>28</b>, stationary case member <b>60</b>; and, permanent magnet <b>64</b>. In the example embodiment of <figref idref="DRAWINGS">FIG. 1</figref> as particularly illustrated, pole member <b>62</b> comprises pole member mating surface(s) (e.g., magnetized mating surface <b>66</b> and magnetized mating surface <b>82</b>). The counter flux generator <b>28</b> is inserted at least partially into the moveable member cavity <b>49</b>. The stationary case member <b>60</b> at least partially defines a case cavity <b>80</b> and comprises the peripheral magnetized mating surface <b>82</b>. Upon insertion of the stationary case member <b>60</b>, the case cavity <b>80</b> is occupied at least partially by the counter flux generator <b>28</b> and pole member <b>62</b>.

0078The method also includes, as act <b>5</b>-<b>4</b>, applying a force which acts (axially) on pole member <b>62</b> for driving pole member mating surface (e.g., magnetized mating surface <b>66</b>) toward moveable magnetically permeable member <b>24</b>, and thereby adjusting central air gap AG<b>2</b> between pole member mating surface <b>66</b> and moveable magnetically permeable member <b>24</b>. The application of the force of act <b>5</b>-<b>4</b> serves to adjust the central air gap AG<b>2</b> independently of the peripheral air gap AG<b>3</b> which exists between peripheral mating surface <b>82</b> of stationary case member <b>60</b> and moveable magnetically permeable member <b>24</b>.

0079In one example embodiment and mode of the method of <figref idref="DRAWINGS">FIG. 5</figref> (illustrated for example by <figref idref="DRAWINGS">FIG. 1</figref>), the method comprises inserting certain elements through the housing mouth in a predefined order. These elements happened to be axially aligned along axis <b>35</b> and each also comprises the magnetic circuit (it being understood that other elements such as stationary case <b>60</b> and moveable magnetically permeable member <b>24</b> also comprise the magnetic circuit). The certain elements which are inserted in the predefined order are pole member <b>62</b>, permanent magnet <b>64</b>, and plate <b>65</b>. The force of act <b>5</b>-<b>4</b> is applied to a selected one of these (e.g., axially aligned) elements upon insertion of the selected one of the axially aligned elements into the housing cavity; and thereafter any remaining one(s) of the selected are inserted into the housing cavity.

0080In an example implementation, the predefined order comprises: pole member <b>62</b>, permanent magnet <b>64</b>; and plate <b>65</b>. In this example implementation, act <b>5</b>-<b>4</b> of applying the force comprises applying the force to the plate <b>65</b>, whereby the force acts consecutively through the plate <b>65</b>, permanent magnet <b>64</b>, and pole member <b>62</b>. In other implementations, the force of act <b>5</b>-<b>4</b> can be applied upon pole member <b>62</b> essentially immediately after insertion of pole member <b>62</b>, with insertion of permanent magnet <b>64</b> and plate <b>65</b> then following. In yet other implementations, the force of act <b>5</b>-<b>4</b> can be applied upon permanent magnet <b>64</b>, with insertion of plate <b>65</b> then following.

0081An example mode of the method further comprises the optional act of inserting, through housing mouth <b>38</b> and into housing cavity <b>37</b> after insertion of the permanent magnet <b>64</b>, an end plate <b>65</b>, and thereby substantially closing housing mouth <b>38</b>. After insertion of the plate <b>65</b> the force of act <b>5</b>-<b>4</b> is applied to plate <b>65</b> instead of to permanent magnet <b>64</b>, whereby the force acts consecutively through plate <b>65</b>, the permanent magnet <b>64</b>, and the pole member <b>62</b> for adjusting the position of stationary magnetically permeable member <b>62</b> along axis <b>35</b> and its magnetized mating surface <b>66</b>.

0082Another example mode of the method further comprises a particular order of inserting components through housing mouth <b>38</b>. In particular, as an optional feature the method can comprise inserting in order through housing mouth <b>38</b>: pole member <b>62</b>; counter flux generator <b>28</b>; stationary case <b>60</b>; and permanent magnet <b>64</b>.

0083Thus, in various embodiments illustrated herein, pole member <b>62</b> is located between moveable magnetically permeable member <b>24</b> and permanent magnet <b>64</b> with respect to axis <b>35</b>. The pole member <b>62</b> comprises a configuration for being selectively positioned through housing mouth <b>38</b> and within case cavity <b>80</b> along the axis whereby the central magnetized mating surface <b>66</b> is positionable along axis <b>35</b> relative to moveable magnetically permeable member <b>24</b> in a manner that is independent of the axial positioning of the peripheral magnetized mating surface <b>82</b> provided on stationary case <b>60</b>.

0084As explained by the method, the air gaps such as air gap AG<b>2</b> and air gap AG<b>3</b> associated with the mid air gap solenoid have been virtually eliminated. The potential for air gaps at the remaining component interfaces has also been virtually eliminated. For example, during the build process assembly method, permanent magnet <b>64</b> is placed in direct contact with pole member <b>62</b> and, due to its magnetic attraction, results in virtually no air gap at air gap AG<b>1</b>. Also, during the build process assembly method, the outer diameter of the plate <b>65</b> is pressed into the inner diameter of a through hole (e.g., case cavity <b>80</b>) in stationary case <b>60</b>, resulting in virtually no air gap at air gap AG<b>4</b>. Moreover, during the build process assembly method, plate <b>65</b> is pressed into the hole (case cavity <b>80</b>) in stationary case <b>60</b> until it contacts permanent magnet <b>64</b>, resulting in virtually no air gap at air gap AG<b>1</b>. Thus, one of the several benefits of the technology is that, when the solenoid is completely assembled, the inherent air gaps of traditional magnetic latching solenoids designs have been virtually eliminated.

0085Traditional magnetic latching solenoids also tend to have variations in the release power supplied by the coil to unlatch the moveable metal component from the stationary component. The primary source of this variation is the inability of the moveable component to repeatedly re-latch against the stationary component in the same position and orientation. The resulting variations in air gaps and magnetic circuits then cause the release power to vary beyond application requirements. But with the present technology, the moveable magnetically permeable member <b>24</b> has a very good bearing surface along the inner surface of housing sidewall <b>34</b>. The housing sidewall <b>34</b> is preferably of plastic, and in smooth fashion guides moveable magnetically permeable member <b>24</b> toward stationary magnetic assembly <b>26</b> during the re-latching process. Thereby, when moveable magnetically permeable member <b>24</b> contacts stationary magnetic assembly <b>26</b>, the contact surfaces between the two components are in consistent and substantial contact area, which reduces release power variations.

0086<figref idref="DRAWINGS">FIG. 6</figref> through and including <figref idref="DRAWINGS">FIG. 13</figref> illustrate other example embodiments which in differing ways and to differing extends implement one or more aspects (but not necessarily all aspects) of the technology of the example embodiment of <figref idref="DRAWINGS">FIG. 1</figref>. In each of <figref idref="DRAWINGS">FIG. 6</figref> through and including <figref idref="DRAWINGS">FIG. 13</figref>, as well as other figures hereinafter described, similar reference numerals are utilized for components or parts that are similar to those of the example embodiment of <figref idref="DRAWINGS">FIG. 1</figref>. In some instances, alphabetical or numerical suffixes are appended to the reference numerals for sake of distinguishing the component or part from a similar component of <figref idref="DRAWINGS">FIG. 1</figref>. Common aspects or similarities of the magnetic latching solenoids of <figref idref="DRAWINGS">FIG. 6</figref> through and including <figref idref="DRAWINGS">FIG. 13</figref> may not be described in detail below, explanation instead primarily being provided for variant or other distinctive aspects or features.

0087The magnetic latching solenoid <b>20</b>(<b>6</b>) of <figref idref="DRAWINGS">FIG. 6</figref> has a mid air gap <b>70</b>(<b>6</b>) in a manner similar to the example embodiment of <figref idref="DRAWINGS">FIG. 1</figref>. In particular, air gap interface <b>70</b>(<b>6</b>) is essentially mid-way between the opposite axial extremities of moveable magnetically permeable member <b>24</b>(<b>6</b>) and stationary magnetic assembly <b>26</b>(<b>6</b>), e.g., mid-way between housing-confined shoulder surface <b>42</b>(<b>6</b>) of moveable magnetically permeable member <b>24</b>(<b>6</b>) and the outer transverse extreme surface of stationary magnetic assembly <b>26</b>(<b>6</b>), e.g., of the stationary case. The magnetic latching solenoid <b>20</b>(<b>6</b>) of <figref idref="DRAWINGS">FIG. 6</figref> also differs from magnetic latching solenoid <b>20</b> of <figref idref="DRAWINGS">FIG. 1</figref> in several ways. As a first example difference, permanent magnet <b>64</b>(<b>6</b>) of magnetic latching solenoid <b>20</b>(<b>6</b>) has an essentially torodial shape and is situated near air gap interface <b>70</b>(<b>6</b>). In fact, permanent magnet <b>64</b>(<b>6</b>) is seated on a notched upper surface of stationary magnetic assembly <b>26</b>(<b>6</b>) and is thereby situated on an outer upper periphery of stationary magnetic assembly <b>26</b>(<b>6</b>) between stationary magnetic assembly <b>26</b>(<b>6</b>) and moveable magnetically permeable member <b>24</b>(<b>6</b>). As a further example, spring <b>30</b>(<b>6</b>) is provided in a central interior cavity <b>100</b> of stationary magnetic assembly <b>26</b>(<b>6</b>). The housing mouth <b>38</b>(<b>6</b>) of housing cavity <b>37</b>(<b>6</b>) is closed by housing cover <b>102</b>. The housing cover <b>102</b> has a central access hole <b>104</b>. The spring <b>30</b>(<b>6</b>) has a first end retained at an intersection of housing cover <b>102</b> and stationary magnetic assembly <b>26</b>(<b>6</b>), and has a diameter greater than that of central access hole <b>104</b>. A second end of spring <b>30</b>(<b>6</b>) bears against the axially extending central portion of moveable magnetically permeable member <b>24</b>(<b>6</b>).

0088The magnetic latching solenoid <b>20</b>(<b>7</b>) of <figref idref="DRAWINGS">FIG. 7</figref> also has a mid air gap <b>70</b>(<b>7</b>) in a manner similar to the example embodiment of <figref idref="DRAWINGS">FIG. 1</figref>, and a permanent magnet <b>64</b>(<b>7</b>) positioned analogous to permanent magnet <b>64</b>(<b>6</b>) of the embodiment of <figref idref="DRAWINGS">FIG. 6</figref>. However, in the example embodiment of <figref idref="DRAWINGS">FIG. 7</figref>, the spring <b>30</b>(<b>7</b>) is retained in a similar manner to spring <b>30</b> of <figref idref="DRAWINGS">FIG. 1</figref>. That is, spring <b>30</b>(<b>7</b>) is retained partially in a central cavity <b>90</b> of moveable magnetically permeable member <b>24</b>(<b>7</b>) and retained partially in a central cavity <b>92</b> of stationary magnetically permeable member <b>26</b>(<b>7</b>). The central cavity <b>90</b> and central cavity <b>92</b> are aligned in the direction of cylindrical axis <b>35</b>. Also in the example embodiment of <figref idref="DRAWINGS">FIG. 7</figref> the spring <b>30</b>(<b>7</b>) surrounds plunger guide post <b>94</b>, which in turn extends centrally through plunger <b>40</b>(<b>7</b>) and is centrally rooted in moveable magnetically permeable member <b>24</b>(<b>7</b>).

0089The magnetic latching solenoid <b>20</b>(<b>8</b>) of <figref idref="DRAWINGS">FIG. 8</figref> also has a mid air gap <b>70</b>(<b>8</b>) in a manner similar to the example embodiment of <figref idref="DRAWINGS">FIG. 1</figref>. Moreover, permanent magnet <b>64</b>(<b>8</b>) is positioned analogous to permanent magnet <b>64</b> of the embodiment of <figref idref="DRAWINGS">FIG. 1</figref>. However, permanent magnet <b>64</b>(<b>8</b>) of <figref idref="DRAWINGS">FIG. 8</figref> is toroidal in shape rather than a solid disk. The permanent magnet <b>64</b>(<b>8</b>) is retained in position in an annular cavity of stationary magnetic assembly <b>26</b>(<b>8</b>). The annular cavity is defined by an axially extending retaining ring <b>106</b>. The permanent magnet <b>64</b>(<b>8</b>) is further retained in the annular cavity by annular-shaped plate <b>65</b>(<b>8</b>).

0090The magnetic latching solenoid <b>20</b>(<b>9</b>) of <figref idref="DRAWINGS">FIG. 9</figref> resembles that of <figref idref="DRAWINGS">FIG. 8</figref>, but differs primarily in that permanent magnet <b>64</b>(<b>9</b>) is disk-shaped (like permanent magnet <b>64</b> of <figref idref="DRAWINGS">FIG. 1</figref>). The permanent magnet <b>64</b>(<b>9</b>) is further retained in the annular cavity by disk shaped plate <b>65</b>(<b>9</b>), like plate <b>65</b> of the <figref idref="DRAWINGS">FIG. 1</figref> embodiment.

0091The magnetic latching solenoid <b>20</b>(<b>10</b>) of <figref idref="DRAWINGS">FIG. 10</figref> resembles that of <figref idref="DRAWINGS">FIG. 1</figref>, in having, e.g., a mid air gap <b>70</b>(<b>10</b>) (in a manner similar to the example embodiment of <figref idref="DRAWINGS">FIG. 1</figref>, as well as an adjustable pole member <b>62</b>(<b>10</b>). Primary differences of the magnetic latching solenoid <b>20</b>(<b>10</b>) of <figref idref="DRAWINGS">FIG. 10</figref> involve the configuration and nature of retention of spring <b>30</b>(<b>10</b>); the structure of counter flux generator <b>28</b>(<b>10</b>); and structure which facilitates provision of separate flux paths for the coil flux (the flux generated by counter flux generator <b>28</b>(<b>10</b>)) and the flux of permanent magnet <b>64</b>(<b>10</b>).

0092The type and location of the spring which separates the two metal components of a magnetic latching solenoid when the solenoid unlatches can be a source of release power variation. Springs with open ends (e.g., pointed ends) tend to push the moving metal component away from the stationary metal component at an angle rather than perpendicular since the two pointed ends of the spring do not apply a force directly on the centerline of each component or in a direction that is parallel with the direction of separation.

0093As shown in <figref idref="DRAWINGS">FIG. 10</figref> and illustrated schematically in <figref idref="DRAWINGS">FIG. 11</figref>, spring <b>30</b>(<b>10</b>) comprises a conical spring situated in the moveable member cavity <b>49</b>(<b>10</b>). The conical spring has a first end coil <b>110</b> (an essentially closed loop) lying in a first spring end plane and a second end coil <b>112</b> (an essentially closed loop) lying in a second spring end plane (see <figref idref="DRAWINGS">FIG. 11</figref>). The second end coil <b>112</b> has a greater diameter than the first end coil <b>110</b>. One end coil of spring <b>30</b>(<b>10</b>) bears against and contacts a radially extending interior surface of the moveable magnetically permeable member <b>24</b>(<b>10</b>); the opposite end coil of spring <b>30</b>(<b>10</b>) bears against and contacts the bobbin <b>72</b>(<b>10</b>), as explained below.

0094Having both spring ends <b>110</b>, <b>112</b> being closed and geometrically grounded applies a more uniform force to the metal components that is more in line with the direction of separation and has a larger “circular” imprint on the moving metal component as compared to the typically used and centrally located standard straight compression spring. This approach not only reduces release power variation but also reduces the average release power because the metal parts separate more “efficiently.” The spring <b>30</b>(<b>10</b>) thereby applies a uniform force with a “circular” imprint having a larger diameter (at second end coil <b>112</b>) and more stably and uniformly drives the moving metal component (e.g., moveable magnetically permeable member <b>24</b>(<b>10</b>)) away from the stationary metal component (e.g., stationary magnetic assembly <b>26</b>(<b>10</b>)).

0095In the example implementation of <figref idref="DRAWINGS">FIG. 10</figref>, flux generator <b>28</b>(<b>10</b>) comprises bobbin <b>72</b>(<b>10</b>). The bobbin <b>72</b>(<b>10</b>) comprises bobbin frame which in turn comprises bobbin cylinder wall <b>74</b>(<b>10</b>), bobbin upper transverse flange <b>77</b>(<b>10</b>), and bobbin lower transverse flange <b>78</b>(<b>10</b>) similar to that previously described with reference to <figref idref="DRAWINGS">FIG. 1</figref>. In addition, for the example embodiment of <figref idref="DRAWINGS">FIG. 10</figref>, bobbin <b>72</b>(<b>10</b>) comprises axially extending bobbin flange <b>120</b>. The axially extending bobbin flange <b>120</b> intersects bobbin upper transverse flange <b>77</b>(<b>10</b>), and both axially extending bobbin flange <b>120</b> and bobbin upper transverse flange <b>77</b>(<b>10</b>) extend into moveable member cavity <b>49</b>(<b>10</b>).

0096In the particular example embodiment illustrated in <figref idref="DRAWINGS">FIG. 10</figref> (and as shown in more detail by <figref idref="DRAWINGS">FIG. 11</figref>), first end coil <b>110</b> of spring <b>30</b>(<b>10</b>) is separated from the moveable magnetically permeable member <b>24</b>(<b>10</b>) by the axially extending bobbin flange <b>120</b>, and is advantageously retained at the intersection of axially extending bobbin flange <b>120</b> and bobbin upper transverse flange <b>77</b>(<b>10</b>). The second end coil <b>112</b> contacts a radially extending interior surface of the moveable magnetically permeable member <b>24</b>(<b>10</b>), e.g., a radially extending interior surface that at least partially defines moveable member cavity <b>49</b>(<b>10</b>). It will be appreciated, however, that in an alternate embodiment or variation that conical spring <b>30</b>(<b>10</b>) can be inverted with respect to its position shown in <figref idref="DRAWINGS">FIG. 10</figref> and <figref idref="DRAWINGS">FIG. 11</figref>, so that in the alternate variation of first end coil <b>110</b> of spring <b>30</b>(<b>10</b>) bears against the radially extending interior surface of the moveable magnetically permeable member <b>24</b>(<b>10</b>) and the larger diameter second end coil <b>112</b> contacts and bears against the bobbin flange <b>120</b> and bobbin upper transverse flange <b>77</b>(<b>10</b>).

0097Thus, the structure of counter flux generator <b>28</b>(<b>10</b>) differs from that of the example embodiment of <figref idref="DRAWINGS">FIG. 1</figref> in having, e.g., axially extending bobbin flange <b>120</b> for accommodating conical spring <b>30</b>(<b>10</b>). The counter flux generator <b>28</b>(<b>10</b>) also differs in having bobbin second lower transverse flange <b>122</b>. The bobbin second lower transverse flange <b>122</b> is parallel to and below bobbin lower transverse flange <b>78</b>(<b>10</b>). As further shown in <figref idref="DRAWINGS">FIG. 10</figref>, lead wires <b>79</b>(<b>10</b>) which supplies electrical current to coil <b>76</b>(<b>10</b>) extends between bobbin lower transverse flange <b>78</b>(<b>10</b>) and bobbin second lower transverse flange <b>122</b>, through an axial aperture in bobbin second lower transverse flange <b>122</b>, axially alongside or proximate the periphery of permanent magnet <b>64</b>(<b>10</b>), through an axial hole in plate <b>65</b>(<b>10</b>), and though an axial port in housing cover <b>102</b>(<b>10</b>).

0098For some applications, it is necessary to minimize the release time for a magnetic latching solenoid to unlatch, e.g. the time from applying power to the solenoid coil in a latched condition to the time when the moving member unlatches, strokes and then reaches the end of its travel. An example of this is application is for circuit breakers which must quickly react to a signal triggered by an overcurrent circuit condition. Quick release times can prevent or minimize catastrophic property damage. When a magnetic latching solenoid is used in this capacity, release times around 5 mSec or less must be achieved.

0099The primary elements that affect release time are the inductance of the coil and solenoid geometry, the mass of the moving member, and the ability of the coil's magnetic flux to become “established” in the magnetic circuit of the solenoid when the coil is energized. The magnetic latching solenoid <b>20</b>(<b>12</b>) of the example embodiment of <figref idref="DRAWINGS">FIG. 12</figref> shows not only how a conical spring <b>30</b>(<b>12</b>) might be packaged into a magnetic latching solenoid, but also shows how a metal pole piece <b>62</b>(<b>12</b>) can be modified to include a large transversal flange <b>130</b>(<b>12</b>) on one end. The dual flux path-facilitating flange <b>130</b> creates a “parallel flux path” to “conduct” both the flux of permanent magnet <b>64</b>(<b>12</b>) [simplistically indicated by flux path FP_Min <figref idref="DRAWINGS">FIG. 12</figref>] and the magnetic flux of coil <b>76</b>(<b>12</b>) [simplistically indicated by flux path FP_Cin <figref idref="DRAWINGS">FIG. 12</figref>] when coil <b>76</b>(<b>12</b>) is energized. The dual flux path-facilitating flange <b>130</b>(<b>12</b>) is in the form of an enlarged annular rim on the periphery of pole member <b>62</b>(<b>12</b>), and in the axial direction extends below bobbin <b>72</b>(<b>12</b>) and air gap about which the flux of permanent magnet travels. An air gap is provided between the outer diameter of the dual flux path-facilitating flange <b>130</b>(<b>12</b>) of pole piece <b>62</b>(<b>12</b>) and the inner diameter of the stationary case <b>60</b>(<b>12</b>) and affects/determines the hold force, and thus the release time.

0100The parallel flux paths allows the magnet's flux to be diverted through an alternative flux path FP_Monce the coil is energized and also allows the coil's flux to become established through a path FP_Cother than through the permanent magnet <b>64</b>(<b>12</b>). Although showing all the flux lines is too complex to depict in <figref idref="DRAWINGS">FIG. 12</figref>, the net result is that the coil's flux is quickly established due to the presence of the parallel path FP_M. As a result, the net attractive force between moveable magnetically permeable member <b>24</b>(<b>12</b>) and stationary magnetic assembly <b>26</b>(<b>12</b>) rapidly decreases and the spring force quickly pushes the moveable magnetically permeable member <b>24</b>(<b>12</b>) away from the stationary magnetic assembly <b>26</b>(<b>12</b>) to the end of travel position for moveable magnetically permeable member <b>24</b>(<b>12</b>). Thus, magnetic latching solenoid <b>20</b>(<b>12</b>) of the example embodiment of <figref idref="DRAWINGS">FIG. 12</figref> also features a response enhancement feature, e.g. a feature that facilitates dual flux paths (separate flux paths for the coil flux (the flux generated by counter flux generator <b>28</b>(<b>12</b>)) and the flux of permanent magnet <b>64</b>(<b>12</b>)).

0101Plunger rotation with an actuation can be a source of release time variations and/or hold force variation for a magnetic latching solenoid. <figref idref="DRAWINGS">FIG. 13A</figref> and <figref idref="DRAWINGS">FIG. 13B</figref> show portions of a magnetic latching solenoid, and particularly portions of housing <b>22</b>(<b>13</b>) and plunger <b>40</b>(<b>13</b>) which have features for counteracting plunger rotation. The features of the various example embodiments described herein are combinable with features of other example embodiments, and accordingly the features of the <figref idref="DRAWINGS">FIG. 13A</figref> embodiment can be combined with the other embodiments described herein and encompassed hereby. In the example embodiment of <figref idref="DRAWINGS">FIG. 13</figref>, a keyed element prevents the moveable member (e.g., the moveable magnetically permeable member) from rotating about axis <b>35</b>. In the particular illustration of <figref idref="DRAWINGS">FIG. 13</figref>, plunger <b>40</b>(<b>13</b>) carries a radially extending key <b>140</b>. The key <b>140</b> extends radially beyond the circumference of the remainder of plunger <b>40</b>(<b>13</b>), and fits into a correspondingly formed groove in plunger aperture <b>36</b> on housing end wall <b>32</b>. The key <b>140</b> can extend axially substantially the length of the plunger <b>40</b>, and slides axially in the accommodating groove. The keyed arrangement prevents plunger <b>40</b>(<b>13</b>), and thus the entire moveable magnetically permeable member, from rotating and thereby becoming a further source of hold force or release force variation. Other keyed or rotation prevention structures are also encompassed, including having an indention or groove formed in the plunger and a corresponding key extending radially into the indentation or groove from the plunger aperture.

0102In the example implementations, the stationary magnetic assembly is distinct from the housing, and the housing is preferably non-magnetically permeable (e.g., plastic, or even brass or aluminum). Thus, in the example embodiments described herein the magnetic latching solenoids have a separate housing to enclose their magnetic components. The housing does not carry magnetic flux nor is it a part of the active magnetic circuit. With typical magnetic latching solenoids, the housing is metal (magnetically conductive) and necessary for proper magnetic operation. In the technology of the embodiments herein described, the housing is only a containment vessel. In some example embodiments, the housing comprises plastic (which allows for mounting features, quieter operation, etc. but when end of travel impact forces get very large, a nonmagnetic metal case (aluminum, brass, etc.) can be implemented.

0103Magnetic latching solenoids need to be flexible in order to meet the customer's application requirements. Factors such as power levels, mounting schemes and the mechanical interfaces to the application need to be considered with every design. The technology described herein allows for flexibility in all those regards. The housing <b>22</b> is preferably plastic and cylindrical in nature to contain the components. A variety of mounting features can easily be molded into the plastic housing.

0104Although one bobbin and coil assembly is shown in the illustrated embodiments (e.g., bobbin <b>72</b> with coil <b>76</b>), the bobbin, coil (wire size, number of turns, etc.) and metal components can easily be modified to accommodate various release power levels for different spring force requirements.

0105Adaptors of different materials and geometries can also be pressed onto the spring guide housing to properly interface with customer applications.

0106By way of review, release power variations and/or hold force variations are most undesirable in a magnetic latching solenoid. The hold force variations are variations in the holding or attracting force of the permanent magnet for the moveable member. Sources of release time variations and/or hold force variation include: 1) plunger rotation with each actuation, 2) mating surfaces which are not flat or parallel, 3) spring forces which cause uneven lift of the moveable member away from the stationary member and 4) bearing surfaces for the moveable member that don't adequately guide the moveable member back to its “original” location.

0107Aspects of the present technology described above have addressed, either alone or in combination, each of these sources. For example, a keyed element (e,g., plunger keyed to an opening in the housing) prevents the moveable member from rotating. Moreover, when the adjustable central core section (e.g., pole member) is pressed into place against the central core of the moveable member, the two members “mate” to better align with their contacting surface. Further, the large outer diameter of a conical spring results in a more uniform lift force as the moveable member releases from the stationary members. Yet further, the large outer diameter and length of the moveable member provide a good bearing surface to guide the moveable member back to its original latch position. Still further, the larger mass of the moveable member in a mid air gap design reduces the impact of the spring pushing the moveable member in a non-preferred direction.

0108Advantages of the technology include but are not limited to the following: <ul id="ul0001" list-style="none"><li id="ul0001-0001" num="0000"><ul id="ul0002" list-style="none"><li id="ul0002-0001" num="0109">Maximization of efficiency of the magnetic circuit by placing the air gap interface (e.g., interface <b>70</b>) in the middle of the metallic and magnetically permeable members of the magnetic latching solenoid.</li><li id="ul0002-0002" num="0110">Reduction in the impact of flatness variations in metal components due to adjustable pole piece.</li><li id="ul0002-0003" num="0111">Virtually elimination of air gaps at all critical interface surfaces due to the assembly process.</li><li id="ul0002-0004" num="0112">Reduction of release power variation due to the design geometry of mating components and bearing surfaces.</li><li id="ul0002-0005" num="0113">A scalable design for different power levels.</li><li id="ul0002-0006" num="0114">Optional mounting configurations and output shaft adaptors.</li></ul></li></ul>

0115Although the description above contains many specificities, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the presently preferred embodiments of this invention. Thus the scope of this invention should be determined by the appended claims and their legal equivalents. Therefore, it will be appreciated that the scope of the present invention fully encompasses other embodiments which may become obvious to those skilled in the art, and that the scope of the present invention is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more.” All structural and functional equivalents to the elements of the above-described preferred embodiment that are known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the present claims. Moreover, it is not necessary for a device or method to address each and every problem sought to be solved by the present invention, for it to be encompassed by the present claims. Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims. No claim element herein is to be construed under the provisions of 35 U.S.C. 112, sixth paragraph, unless the element is expressly recited using the phrase “means for.”